In the road bicycle market, there are primarily two cranksets types: standard and compact. Compact cranksets can typically offer a lower gear ratio than standard cranksets. Both of these crankset types employ the same basic configuration, which has been standardized on cranksets for decades. This configuration consists of a series of chainring bolts and chainring nuts that jointly fasten a large chainring and a small chainring together and trap a spider of the crankset between the two chainrings. Cranksets can also have a single chainring or more than two chainrings. In this manner, the chainrings are fixed to the chainring spider of the crankset With this approach, the chainring bolts holes in the chainrings and corresponding holes in the spider must line up so that the mating pairs of the chainring bolts and chainring nuts can bass through both chainrings and the spider and engage each other. These chainring bolt holes in the spider form a circular pattern called a bolt circle, which is concentric with a rotational axis of the crankset.
A skilled person will appreciate that the weight of a bicycle is extremely important, especially for a competitive cyclist or bicycle racer. Because bicycles are manually powered, weight has a tremendous effect on energy utilization and performance in powering a bicycle. Furthermore, because a crankset is one of the more large and heavy components of a bicycle, reducing weight of a crankset can significantly impact the overall weight of the bicycle. Still further, because of the rotational movement of the crankset for the purpose of transferring power to the rear wheel of a bicycle (e.g., via a chain), weight of the crankset can have a significant impact on the energy required to rotationally accelerate the crankset from one rotational speed to another. This can be quite important to a competitive cyclist or a bicycle racer as it influences how quickly and efficiently they can accelerate their bicycle from one road speed to another.
Although weight of the crankset is important, flexural stiffness of the cranks is also important. A crankset that is quite light, but that exhibits considerable flexure when being pedalled will generally exhibit less than optimal performance. This is because flexing within any element of the crankset will typically result in the loss of energy that would otherwise contribute to powering the bicycle. Accordingly, weight of the crankset must be balanced with its flexural stiffness.